[Yang Nak-gyu's Defence Club] 'North Korea's Test of Combining Nuclear Warheads with Solid-Fuel Missiles Remains'

Interest in North Korea's solid-fuel technology has increased recently as it conducted its first test launch of a ballistic missile estimated to use solid fuel, with a range of medium or longer.

According to the military on the 15th, North Korea fired one ballistic missile toward the East Sea from near Pyongyang at around 7:23 a.m. on the 13th. The flight distance was about 1000 km with an altitude below approximately 3000 km, which is a specification not seen in previous launches of intermediate-range ballistic missiles (IRBM) or intercontinental ballistic missiles (ICBM).

Adding the missile's launch characteristics and trajectory shape, the military's initial analysis concluded that this launch was a test of a new weapons system. In particular, it is considered highly likely that solid fuel was used. Solid-fuel missiles produce launch flames that spread outward, whereas liquid-fuel missiles have flames concentrated like a candle flame. Because solid fuel provides strong instantaneous thrust, the ascent speed is faster than that of liquid-fuel missiles. It is known that South Korea and the U.S. detected these differences.

[Image source=Yonhap News]

Ballistic missiles are classified into ground-launched and submarine-launched missiles, and further subdivided by range into short-range ballistic missiles (50-300 km), medium-range ballistic missiles (300-1000 km), intermediate-range ballistic missiles (1000-3000 km), intermediate-to-long-range ballistic missiles (IRBM/3000-5500 km), and intercontinental ballistic missiles (ICBM/over 5500 km). Additionally, there are differences depending on whether solid or liquid fuel is used.

North Korea's First Solid-Fuel Missile

North Korea's first missile to use solid fuel was the short-range ballistic missile Doksa (KN-02). It has a maximum range of 120 km and was developed based on Russia's Tochka missile. Later, after importing the Scud-B missile (range 300 km) from Egypt in 1976, North Korea began missile development through reverse engineering and succeeded in developing a Scud-B replica in 1984. Subsequently, in 1986, it test-fired a Scud-C replica with a range of 500 km and began operational deployment of these missiles from 1988. Building on this experience, in the 1990s, North Korea deployed the Nodong missile with a range of 1300 km capable of striking Japan and started developing long-range missiles.

From the First Solid-Fuel Missile Doksa (KN-02) to Completing the ICBM

In 1998, North Korea conducted its first long-range missile test launch of the Taepodong-1 (range 2500 km). The name 'Taepodong-1' was given by South Korea and the U.S., while North Korea announced it had successfully placed its first satellite, Kwangmyongsong-1, into orbit. Subsequently, North Korea test-fired the Taepodong-2 in 2006, estimated to have a range exceeding 6700 km, and launched Taepodong-series long-range missiles disguised as satellites in 2009 and twice in 2012. In December 2012, during the launch of the Unha-3, it succeeded in three-stage separation. Since 2012, North Korea has also unveiled the KN-08 and its improved version KN-14, ICBM-class missiles estimated to have ranges over 9000 km.

From the late 1990s, North Korea focused on developing longer-range intermediate-to-long-range missiles, succeeding with the Hwasong-10 (Musudan) and then test-firing the Hwasong-12 with a range of 5000 km in 2017. Soon after, it advanced to test launches of intercontinental ballistic missiles. In July 2017, it successfully test-fired the Hwasong-14 twice, with a range of 10,000 km, and in November of the same year, it succeeded in the test launch of the Hwasong-15.

[Image source=Yonhap News]

On October 10, 2020, at the 75th anniversary parade of the founding of the Workers' Party of Korea, a ballistic missile never seen before was unveiled for the first time. In October 2021, at North Korea's weapons exhibition 'Self-Defense-2021,' it was revealed that the official designation of this missile is Hwasong-17 (North Korea's official name is 'Hwasongpo-17').

On November 18, 2022, the Joint Chiefs of Staff announced that North Korea conducted a high-angle launch of an ICBM estimated to be the Hwasong-17, sending it up to about 6100 km. If launched at a normal angle (30-45 degrees), the range was estimated to exceed 15,000 km. This is longer than the strategic strike range to the U.S. mainland (13,000 km), and the Hwasong-17 can be equipped with multiple warheads, amplifying its threat. Therefore, the Hwasong-17 is sometimes called the 'monster ICBM.'

On the 17th of last month, North Korean state media Korean Central News Agency reported that Chairman Kim Jong-un personally supervised a Hwasong-17 launch drill the previous day. The agency stated, "The intercontinental ballistic missile 'Hwasongpo-17' launched from Pyongyang International Airport ascended to a maximum apogee of 6045 km, flew a distance of 1,000.2 km for 4,151 seconds, and landed in the target area in international waters of the East Sea."

Advantages of Solid-Fuel Missiles

Solid-fuel ICBMs are one of the 'five major tasks' in the five-year plan for national defense development presented by Chairman Kim Jong-un at the 8th Congress of the Workers' Party of Korea in January 2021.

At that time, Kim Jong-un proposed the five major tasks as ▲ development of hypersonic weapons ▲ production of super-large nuclear warheads ▲ improvement of strike accuracy within a 15,000 km range ▲ development of underwater and ground-based solid-fuel intercontinental ballistic missiles (ICBM) ▲ possession of nuclear submarines and underwater-launched nuclear strategic weapons. Regarding solid-fuel ICBMs, North Korea claimed last December to have succeeded in the first ground static test of a high-power solid-fuel engine with a thrust of 140 tf (ton-force) at the Dongchang-ri West Sea Satellite Launching Station in Cholsan County, North Pyongan Province.

North Korea is enthusiastic about developing solid-fuel missiles because they have many advantages over liquid-fuel missiles. Using solid fuel allows missiles to be mounted on mobile launchers (TEL) for surprise launches. TELs carrying missiles can be quickly launched anytime and anywhere and can hide in tunnels, reducing the likelihood of being struck, which is a military advantage.

If North Korea uses liquid fuel for ICBMs, they must be launched within a week. Unlike solid fuel, liquid fuel cannot be used after one week due to oxidation and other effects after fueling, requiring refueling.

If liquid fuel is used, oxidizers must also be added, increasing the chance that launch signs will be detected by reconnaissance satellites of other countries. However, solid fuel mixed with oxidizers is preloaded into the propellant, eliminating the need for separate fueling procedures. This means it can be launched immediately at any time. Additionally, the oxidizers in liquid fuel are highly toxic substances that make long-term storage difficult once loaded into the missile, whereas solid fuel is integrated with the warhead and can be stored or transported for over 10 years.

If a Nuclear Warhead Is Mounted on a Solid-Fuel Missile

North Korea revealed what is presumed to be an 'amplified nuclear fission warhead' for the Hwasong-13 in 2016 and a 'hydrogen bomb' warhead for the Hwasong-14 in 2017. Last month, it unveiled a 'tactical nuclear warhead' for the first time, called Hwasan-31. If North Korea's claims are true, this raises the threat level aimed at South Korea to the maximum.

According to North Korea's disclosure, the tactical nuclear warhead Hwasan-31 is estimated to have a warhead diameter of 40-50 cm and can be mounted inside the 600 mm super-large multiple rocket launcher (KN-25). It can also be equipped on the North Korean versions of the Iskander (KN-23), Hwasal-2 cruise missile, unmanned underwater attack vehicle 'Haeyil,' Hwasal-1 cruise missile, North Korean version of the ATACMS (KN-24), and the 'Mini' submarine-launched ballistic missile (SLBM).

However, military authorities remain skeptical about North Korea's nuclear capabilities. Lee Sung-jun, spokesperson for the Joint Chiefs of Staff, explained, "To consider (North Korea's) nuclear capability fully operational, it must succeed in tests under conditions identical to actual use. Since nothing has been confirmed yet, we are evaluating whether it can be used as a weapon."

Some speculate that North Korea's unveiling of tactical nuclear warheads may signal the possibility of a 7th nuclear test. Given that North Korea has conducted the 5th and 6th nuclear tests shortly after revealing nuclear warheads in the past, this possibility is considered realistic.

Olli Heinonen, former Deputy Director General of the International Atomic Energy Agency (IAEA), said in November last year to Voice of America (VOA), "For North Korea, which possesses tactical nuclear weapons, medium-range ballistic missiles, and intercontinental ballistic missiles (ICBM), multiple tests will be necessary to meet the requirements of an ambitious nuclear weapons program."

This content was produced with the assistance of AI translation services.